Do you have more information about it? By googling "Linux platypus" the only thing that I could find is that exact URL

The Tux penguin was suggested as the unofficial logo for the 2.0 release of Linux, which had SMP support and was a big deal. It half-jokingly received Linus' blessing and everyone has used it since.

It's easy to see why, it is an instant classic, very cute, and works in different situations and at different scales. Larry Ewing who drew the picture, a sysadmin and not a professional illustrator, still has a web page up describing it: https://isc.tamu.edu/~lewing/linux/

Before that there were many logos but the platypus one was probably the most used. Walnut Creek, who put out CDROMs with shareware and freeware, used to publish the popular Linux distributions too and they needed something for their covers and used it.

Slackware kept using it for a long time. I believe the idea was that Linux, too, looks like it was put together by disparate parts. Web pages back in 1996 was mostly textual and pictures were used sparingly so the use case was mostly books and CDROM covers. There is a certain cuteness to it and it did look good on T-shirts.

If you google for slackware 96 cd youll find a similar one. :)